Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine or a printer, a cartridge detachably mountable to such an image forming apparatus, a displaying method for displaying a developer remainder, and a developer remainder displaying system, more particularly to an image forming apparatus for correctly displaying the remaining amount of the developer, a cartridge detachably mountable to such an image forming apparatus, and a developer remainder displaying method and a developer remainder displaying system.
Here, examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (a laser beam printer or an LED printer mountable), a facsimile machine, a word processor and the like.
The process cartridge integrally contains an electrophotographic photosensitive drum, and charging means, developing means or cartridge, in the form of a unit or a cartridge, which is detachably mountable to a main assembly of an image forming apparatus.
Heretofore, in an electrophotographic image forming apparatus using the electrophotographic image process, a process-cartridge type in which the electrophotographic photosensitive member and process means actable on the electrophotographic photosensitive member are integrally contained in a cartridge, is detachably mountable to the main assembly of the image forming apparatus. In such a process-cartridge type, the maintenance of the apparatus can be carried out by the users without a serviceman, and therefore, the operativity can be improved significantly, and for this reason, it is widely used in the image forming apparatus. Therefore, the process cartridge type is widely used in the field of the electrophotographic image forming apparatus.
With such an electrophotographic image forming apparatus of the process cartridge type, when the developer is used up, the cartridge is exchanged, and the images can be formed, but the exchange of the cartridge has to be carried out by the user, so that a developer amount detecting device is to be provided to notify the user of the shortage of the developer.
In order to provide information about the remaining amount of the developer, the cartridge or the main assembly of the image forming apparatus is provided with developer remainder detecting means for detecting the developer remainder.
An example of such developer remainder detecting means is an electrostatic capacity detecting-type means. An antenna for detection of the developer remainder is disposed in the developer accommodating container, and an AC voltage is applied to the electrode provided at a predetermined position, by which an electric current is produced in the antenna in accordance with the amount of the developer existing between the electrode and the antenna. The developer remainder is detected on the basis of the change of the current.
For example, a flat antenna type is known, which is an electrostatic capacity detecting type detecting member. As shown in FIG. 3, the flat antenna comprises a pair of electroconductive patterns 22, 23 on a substrate 21 with a predetermined clearance therebetween. It is disposed at a position for contact with the developer at an inner side surface of the developer accommodating container, for example. With the decrease of the developer in the developer accommodating container, the contact area between the developer and the flat antenna 20 decreases.
With the consumption of the developer, the contact area between the developer and the surface of the electroconductive pattern changes, so that the electrostatic capacity therebetween changes, and therefore, the developer remainder in the container and the electrostatic capacity of the flat antenna correspond to each other. By measuring the electrostatic capacity of the flat antenna, the developer remainder in the container can be known.
Another type of electrostatic capacity detecting type detector is used with a so-called jumping development system wherein an AC bias is applied to the developing roller, which is a developer carrying member disposed in the developer accommodating container, by which a latent image on the photosensitive member is developed. The detector is a plate antenna type comprising a plate (plate antenna) provided in parallel with the developing roller.
It uses the change of the electrostatic capacity between the plate antenna and the developing roller in accordance with the amount of the insulative developer present between them. When the space between the plate antenna and the developing roller is filled with the developer, the electrostatic capacity is large, and with the decrease of the developer, the air in the space increases so that electrostatic capacity decreases. Therefore, the amount of the developer can be detected by a relation between the electrostatic capacity between the plate antenna and the developing roller and the amount of the developer.
By providing the developer accommodating portion, that is, the developer accommodating container with the developer remainder detecting means, the developer remainder can be detected substantially in real time, and simultaneously, it can be known substantially in real time how many image formations can be performed.
Another detecting means for the developer remainder is a torque detecting type detecting means in which developer stirring means is provided in the developer accommodating container, and the developer remainder is detected using the change of the load of the developer stirring means in accordance with the developer remainder.
Recently, with the change in the office environment resulting from the wider use of the personal computers, the print volume, which is the number of uses of the image forming apparatus by the users and the number of prints per unit time, has tended to increase. With such a tendency, the frequency of the exchanges of the process cartridges increases, and the exchanging operations and the cost required therefor have become a problem.
As a countermeasure, a large capacity process cartridge has been developed that has a longer nominal lifetime because of the larger amount of the developer in the developer accommodating container despite the fact that configuration and the size are the same as the normal process cartridge, both of them being usable with the same image forming apparatus.
Here, the term “nominal lifetime” means the number of sheets on which images can be formed by one process cartridge on the assumption that the print ratio is standard for all images (5%).
The user can selectively use the normal process cartridge or the large capacity process cartridge in view of the situations, thus permitting the load and cost required by the exchange of the process cartridge to be reduced.
However, if the process cartridges having the different amounts of the developer in the developer accommodating containers are alternately used, the correct display of the developer remainders in the developer accommodating container of the process cartridge has not been accomplished.
When the remaining amount of the developer is displayed on a display of the printer or on a display of a personal computer, the displayed information is desirably easy to understand. It is desirable to display the remaining amount in the form of a bar graph, a circle graph or numerical graph, and it is particularly preferable to display it in a percentage.
Doing so involves the following problems.
For example, the case will be described in which the normal cartridge S having a nominal lifetime of 5000 sheets and the large capacity cartridge L having a nominal lifetime of 10000 sheets are available, the two types of the process cartridges are usable with the one and the same image forming apparatus. In such a case, in the cartridge S, the toner is filled only up to half of the full height of the flat antenna, as shown in FIG. 3, and in the cartridge L, the toner is filled up to the top end of the flat antenna.
It is desirable that the remaining amount display level of the cartridge S originally before the start of use is 100%, but the actual display level of the remaining amount is 50%. This is because the toner is only up to one half the flat antenna height. This will confuse the user, since the unused process cartridge is displayed as containing only one half the complete amount of developer.
Furthermore, in some cases, a cartridge, which may have a different nominal capacity than that of the cartridge first put on sale, may later be put on the market because of demands therefrom. In consideration of such a case, it is desirable to develop a developer remainder notifying function capable of covering the unknown future nominal lifetime of the process cartridge.
Therefore, it would be desirable to provide means capable of notifying the user in substantially real time of the correct developer remainder amount for each of the process cartridges having different nominal lifetimes.
By using such developer remainder detecting means, the developer remainder level in the developer accommodating container can be known in substantially real time by the user, and it is possible to notify the user of the fact that cartridge-exchange timing is approaching.
The user has to prepare a fresh process cartridge before the depletion of the developer (incapability of image formation). Therefore, the warning-generation timing is determined in view of the printable number before the cartridge becomes incapable of printing.
If the time period or the printable number before the cartridge becomes incapable of printing is different depending on the process cartridges, the time given to the preparation is not constant, thus causing a deterioration in usability.
It is therefore desired to provide the proper timing warning to the operator despite the use of process cartridges having different nominal lifetimes.